A method for manufacturing a laminated body has heretofore been known, in which a transparent conductive layer peelably laminated on a temporary supporting body is transferred to a transparent substrate composed of plastic material through an adhesive agent, thereby producing a laminated body including the transparent substrate and the transparent conductive layer. Such a transparent conductive layer is typically composed of an indium tin oxide (ITO).
For example, Japanese Patent Application Laid-Open No. S60-231396 discloses a transfer type laminated body in which an ITO layer is peelably formed on a temporary supporting body. This Laid-Open further discloses a method in which an ITO layer is vapor-deposited on a supporting body composed of a Teflon film, thereafter, the vapor-deposited ITO layer is subjected to heat treatment in an oven at a temperature of 300° C. to decrease the electrical resistance of the ITO layer, and the ITO layer of the transfer type laminated body is transferred to a polymethyl-methacrylate substrate. It also teaches that an aromatic polyimide can be used as the supporting body. Moreover, Japanese Patent Application Laid-Open No. S59-204542 discloses a method in which an ITO layer is vapor-deposited to a heat-resisting substrate which has been subjected to peel-off treatment and thereafter, the ITO layer is transferred to a film through an epoxy resin adhesive agent having a low temperature hardening property.
Japanese Patent Application Laid-Open No. S58-177345 discloses a method in which an ITO layer is sputtered to a mold release treatment surface of a polyester film, and the ITO layer is thermally press-bonded to a polyvinyl butyral sheet so that the ITO layer is transferred to the surface of the polyvinyl butyral sheet.
Japanese Patent Application Laid-Open No. S59-151705 discloses a method in which an ITO vapor-deposited film layer is formed on a temporary carrier such as a Teflon film and a polyimide film and then the ITO layer is transferred to a surface of a plastic transparent substrate through an adhesive agent having a thermo- or photo-hardening property.
Moreover, Japanese Patent Application Laid-Open No. H07-80980 discloses a transparent conductive transfer sheet in which an ITO layer and an adhesive layer are sequentially laminated on a substrate composed of a film having a low surface energy. It also teaches a stretched polypropylene as a specific example of a film having a low surface energy.
On the other hand, Japanese Patent Application Laid-Open No. H02-174011 discloses a method in which a resin coating film is laminated on a temporary supporting body (release sheet), an ITO layer is laminated on the resin coating film and a thermally adherable adhesive agent is laminated on the ITO layer to thereby form a transfer sheet, and the transfer sheet is press bonded to a glass substrate while heating, so that a laminated body composed of the ITO layer and the resin coating film is transferred thereto through the adhesive layer. This Patent Application Laid-Open teaches that a synthetic resin film such as polyethylene, polypropylene, polyester and the like can be used as the supporting body and the a mold releasing treatment is executed, where necessary, with respect to the supporting body. It is also disclosed that a peelable layer functions as a protective film of the ITO layer that as a suitable material thereof, one can be selected from the group consisting of celullosic resins, acrylic resins and nylon resins and that the thickness of the peelable layer is 1.5 μm or less and preferably 1 μm or less.
Furthermore, Japanese Patent Application Laid-Open No. H11-24081 discloses a method in which a laminated body including polyimide resin layer and an ITO layer laminated on a temporary carrier by vapor-deposition, sputtering, pasting or the like is peeled off from the polyimide resin layer and transferred. It also teaches that a film having a heat-resisting property such as kapton, polyetherimide, etc. is used as a supporting body. At that time, the polyimide resin layer is also transferred from the temporary carrier to the transparent substrate and this polyimide resin layer is formed to have a thickness of 100 nm suited to be used as an orientation film.
In the above-mentioned conventional methods, an ITO layer is formed on a heat-resisting plastic film and then transferred to a plastic film or glass substrate through an adhesive agent. Accordingly, no consideration is paid to the variation (expansion and contraction) of the film occurrable at the time of formation of the ITO layer on the plastic film.
Moreover, this adverse effect becomes more manifest as the pattern precision of the ITO layer becomes finer. However, the conventional methods pay no attention to this fact.
For example, in the series of a transfer laminated body and a transfer method discussed in the former method, the ITO layer is laminated directly to the temporary supporting body and no resin layer is disposed together with the ITO layer between the supporting body and the ITO layer. In a constitution like this, it is practically impossible to etch the ITO layer on the supporting body so as to form a pattern. The reason is that since the adhesion between the ITO layer and the underground layer is not good, an etching liquid is liable to permeate into an interface between those layers at the time of an etching treatment to the ITO layer and as a result, the patterned ITO layer is peeled off.
In the latter method, the ITO layer is formed on the plastic film as a supporting body. Accordingly, when the ITO layer is shaped into the form of a pattern in that state, the plastic film is expanded and contracted by thermal expansion and/or temperature at the time of formation of the pattern. This makes it impossible to form an ITO layer with a high degree of precision.
Moreover, since a plastic film is used as the supporting body, another problem is encountered in which a long dimensional accuracy cannot be obtained due to distortion of the film. Particularly, in the case where a color filter is formed on the ITO layer, it is necessary to make a positional alignment between the ITO layer and the color pixels constituting the color filter or between the color pixels. However, if the pattern precision (positional precision) is not good, there is such a vital shortcoming in that the color pixels cannot be provided on the ITO layer correctly.
For example, the thermal expansion coefficient of polyimide (Kapton) as a representative heat-resisting high polymer is about 4×10−5/° C. This means that if the temperature is changed 1° C., a film (polyimide) having a length of 30 cm is expanded by 12 μm.
However, it is difficult to control the temperature within a range of 1° C., in the actual manufacturing process. Also, if it is taken into consideration the fact that a space width of the adjacent lines of ITO for a crystal device is normally 10 to 20 μm, there can be encountered with such inconveniences that due to variation of the heat processing temperature at the time of manufacture, a color pixel of the color filter layer is overlapped with a different color pixel or placed astride over different color pixels.
As an example of the change in length dimension due to variation of temperature, one test example is taken up here, in which a film composed of a polyether sulfone resin was used. Only by dipping this film in water for cleaning, the length of 30 cm was elongated 150 μm. This film was treated at 100° C. for drying and the temperature was then returned to a normal temperature. As a result, the film was contracted by 300 μm compared with the length before washing. This film was stored at a constant temperature and humidity, three days were required until the length gets stabilized. If the length dimension of the film is so extensively changed as just discussed, a difficulty is accompanied with not only the positional alignment at the time of manufacture of the ITO and color filter layers but also the positional alignment between the ITO and a driver circuit.